The present invention relates generally to antennas for use in wireless communication systems. More particularly, the present invention relates to multiple purpose antennas used in vehicles and crafts having both global positioning systems and cellular telephone systems.
The expansion of mobile and personal cellular telephone systems has been rapid and widespread during the last few years. Originally, cellular telephone systems were designed to provide communication services primarily to vehicles and thus replace mobile radio telecommunication systems. Advancements in technology and production have sufficiently decreased the costs of cellular service to the point at which cellular telephone service has now become affordable to a majority of the general population. Therefore, a "cellular" telephone system no longer strictly refers exclusively to cellular telephones, which originally were physically attached to and made a part of the vehicle. A cellular telephone system now also includes portable, personal telephones which may be carried in a pocket or a purse and which may be easily used inside or outside a vehicle or building.
Traditionally, wireless communication systems have included antennas that transmit and receive radio frequency ("RF") signals within the NAMPS band of frequencies in the United States or the GSM band of frequencies in Europe. Wireless communication systems which operate in the NAMPS or GSM frequency bands generally operate in a relatively low frequency band. The NAMPS bandwidth used for conventional cellular communication in the United States extends from about 824 MHz to about 894 MHz. The GSM bandwidth used for conventional cellular communication in Europe extends from about 872 MHz to about 960 MHz.
The wireless communications industry has recently broadened the scope of communication services by providing small, inexpensive, hand-held transceivers that transmit and receive voice and/or data communications, notwithstanding the geographic location of the user. These newer communication systems are also considered as cellular systems and operate within higher frequency bands than the NAMPS/GSM frequency bands and have generally been referred to as a personal communication network (PCN) and/or a personal communication system (PCS). The PCN and PCS-type systems are wireless communication systems which, for all intents and purposes, eliminate the need for separate telephone numbers for the home, office, pager, facsimile or car.
With the recent surge in the use of wireless communication devices, a need has grown to extend the capacity and to improve the communication quality and security of wireless communication systems. As such, several countries and communication providers have agreed upon international communication standards and set aside a portion of the ultra-high frequency microwave radio spectrum as frequency bands which are dedicated exclusively for PCN and PCS communication systems.
On a worldwide basis, the PCN, PCS and JTACS (used in Japan) frequency bands extend from about 1.4 GHz (1500 MHz) to about 2.4 GHz (2400 MHz). Within those bands, individual countries have set aside particular portions of it for their respective wireless communication systems. For example, Japan, which uses JTACS, has set aside from about 1.429 GHz (1429 MHz) to about 1.521 GHZ (1521 MHz), Europe, which uses PCN, has set aside from about 1.710 GHz (1710 MHz) to about 1.880 GHz (1880 MHz) and the United States, which uses PCS, has set aside from about 1.850 GHz (1850 MHz) to about 1.990 GHz (1990 MHz).
The bandwidths of the above different frequency bands represent approximately forty percent (40%), or only about 400 MHz, of the total possible bandwidth set aside for the higher frequency band wireless communication systems. The lowest frequency included within this bandwidth is almost two times higher than the standard frequency at which cellular telephone communication systems operate within the United States, namely 800 MHz, i.e., the NAMPS frequency band. Wireless communication systems operating in the PCN, PCS or JTACS frequency bands have improved communication quality and strengthened security over those systems which utilize the lower frequency bands.
An ever increasing number of regions now utilize the PCS (United States), PCN (Europe) or JTACS (Japan) frequency bands for wireless communications. In most of those regions, wireless telephone units must be able to operate in both the higher and lower frequency bands, i.e., in both the NAMPS and PCS frequency bands in the United States, and in both the GSM and the PCN frequency bands in Europe, so that a user of such units may selectively choose the frequency band of operation for the unit. Additionally, the units themselves may selectively choose their operating frequency band so that the chosen band matches the frequency of the electromagnetic signals received from a wireless telephone unit placing an incoming call to that particular unit.
In a different wireless application, electromagnetic signals are often used in tracking and global positioning systems. The NAVSTAR Global Positioning System (GPS) is a Department of Defense satellite navigation system that uses a constellation of GPS navigation satellites in a space segment (SS) to transmit GPS signals and data from which a GPS receiver may derive accurate position, velocity and time information with respect to the position of a person, vehicle or craft.
A GPS control segment on the ground tracks the SS satellite constellation, and uplinks to each GPS satellite ephemeral data regarding its orbital characteristics and satellite clock correction parameters to precisely synchronize the on-board satellite atomic clock with reference to GPS system time. Each GPS satellite continually transmits a navigation signal that provides navigation message data, including time of transmission, satellite clock correction parameters and ephemeral data.
The navigation signal is transmitted over two carrier frequencies in the L band (L1 at 1575.42 MHz and L2 at 1227.6 MHz). This navigation signal includes latitude, longitude, altitude and timing data for marine, aerial and mobile tracking information. Reception of this navigation signal permits a GPS receiver to identify and track its global position. This GPS technology provides tracking information for vehicles, crafts and even persons that carry GPS locating devices.
These GPS systems are now being incorporated in automobiles, trucks and to provide location and travel information to the operator. They are also used in other vehicles, such as farm tractors to indicate the exact position of the tractor (and any implements it tows) to the farmer. Similarly, the use of GPS systems is increasing in watercraft. In all these applications, the operator of the vehicle or craft may often utilize a cellular telephone. Presently, a separate antenna is needed for the GPS locator and for the cellular telephone. The use of two separate antennas for the cellular and GPS systems unduly complicates the exterior profile of the vehicle or craft.
It is therefore desirable to develop antennas that may transmit and receive electromagnetic signals in all of the above-identified frequency bands.
Previous multi-band antennas have been designed to transmit and receive electromagnetic signals in the AM/FM and the NAMPS cellular operating frequencies. These previous multi-band antennas are useful in that they minimize the number of radiating elements that are required to operate equipment in those frequency bands. However, their use has been limited to operation within those lower frequency bands due to their inherent narrow bandwidth. The use of multi-band antenna technology at operating frequencies higher than AM/FM and NAMPS has not yet been feasible. In particular, the multi-band frequency antennas have not yet been operable in the GSM (872-960 MHz), PCN (1710-1880 MHz), PCS (1850-1990 MHz) and JTACS (1429-1521 MHz) frequency bands. With the increasing popularity of other applications for wireless technology, such as GPS (1574-1576 MHz), it is desirable to create a single antenna that can provide tracking and voice/data communications simultaneously. A combined GPS/cellular solution for this purpose is the focus of this invention.